Borax

A white or colorless crystalline mineral composed of hydrated sodium borate, used as a flux, cleansing agent, tanning agent, water softener, preservative, fungicide, as an alkaline ingredient in glass, ceramics, and glazes, in soldering, and as a source of boron. Borax is produced by the evaporation of water in shallow lakes. Borax was used by the Egyptians for mummification, by the Romans for glassmaking, as a flux for soldering gold in 9th-century Arabia, in ceramic glazes in northern China in the 10th century, and in Venetian glass from the 13th century.